A conventional gas control system is shown in FIG. 36. In the gas control system, an inspection meter 50 incorporating a microcomputer is provided with a valve 52. The valve 52 is connected at an inlet 54 thereof with a city gas supply source or a gas tank through a gas supply pipe 56, and at an outlet 58 thereof with such gas appliance 62 as hot water supply system through a gas distribution pipe 60, so that a gas forwarded from a gas supply source is supplied through the valve 52 to the gas appliance 62. The inspection meter 50 is also provided with a control unit (not shown) for cutting off supply of the gas by closing the valve 52 when such abnormal condition as gas leakage and abnormal pressure or flow rate of the gas is detected and a reset button (not shown) for returning the valve in a closed position to an open position. On the other hand, the gas appliance 62 is connected with a remote controller 64, and can be controlled by means of a command from the remote controller 64.
Another conventional gas control system is shown in FIG. 37. The gas control system comprises a terminal network controller 70 for communicating with a remote control center 68 through such communication medium 66 as telephone line, and an inspection meter 50 and a gas appliance 62 are connected with the terminal network controller 70 by communication media 72, 74, respectively, so that information obtained from the inspection meter 50, that is, information on a consumption of gas and information of abnormality in the gas appliance can be communicated to the remote control center 68.
However, any of the gas control systems is not constituted in such manner that the inspection meter and gas appliance are controlled according to information from one another, and the gas appliance is maintained in a combustion enabled state even after the valve is closed due to such abnormal condition as abnormal flow rate of the gas. Thus, it has been hard to say that a sufficient level of safety can be assured in such gas safety control systems. In addition, when the valve is closed, since no gas is supplied to the gas appliance, an abnormal condition (error) is caused, which is regarded as abnormality in the gas appliance even though no abnormality is present in the gas appliance, and it has been required to turn on the power again in order to restore operation of the appliance. It has also been a problem that an operating state of the gas appliances as well as that of the inspection meter cannot be easily known.